Sunday: 9 a.m. to 5 p.m. Street Fair. 9 a.m. to 2 p.m., the U.S. Open Sandcastle Competition. Professional and amateur teams compete for more than $21,000 in cash prizes. 4 p.m., awards ceremony. Masterpieces are available for viewing only until 4 p.m. because of the tides.

Where: Pier Plaza at the intersection of Seacoast Drive and Evergreen Avenue, Imperial Beach. ﻿Seacoast Drive is closed for the event.

Tickets: Admission is free; $55 to $80 to register a team for the competition

If you are planning on attending the U.S. Open Sandcastle Competition on Sunday, expect something a bit more intense than typical sand castle building.

“I love the competition,” said Leonard Gonzales Jr., captain of the local I.B. Posse. “It definitely brings in a different element than the leisure of piling sand up and spending a day at the beach.”

Gonzales and his team are hoping to continue as reigning champions, but the rivalry between I.B. Posse and Archisand is as fierce as ever.

“We are positioned to do well. We have a good group of people,” said Gregory LeBon, founder of the Orange County-based Archisand. “This year, we have a stronger team, and I feel good about that.”

While more than 40 teams are fighting for the title of Master’s Champion, I.B. Posse and Archisand usually dominate the top two positions. The teams have been battling since 2000.

The key to this friendly rivalry? Lots of practice.

“We hold practice twice a week, usually three or four weeks before the contest,” Gonzales said. “At each practice, we focus on special features of the design so we can get better.”

Archisand seems to do the same. “We do a complete mock trial,” LeBon said by phone Monday. “Yesterday, we got through almost all of it, so I’m very happy about that.”

The creations made by Archisand and I.B. Posse are known for extreme attention to detail.

“The worst moment is at hour four, and someone is saying ‘It’s a cow. No, it’s a pig.’ ‘What is it?’ ” LeBon confessed. “If you get too much of that, then you are through. We have to work quickly to create a piece that has the audience wanting to see more.”

The two teams also make a point to connect with the audience through their piece.

“I think if the piece is relevant to any common topic of the times, it can make a difference between a win and a loss,” said Gonzales, who won last year’s competition with a sculpture titled “Got Oil.” The piece referenced the 2010 BP oil spill that ravaged the Gulf Coast.

More than 350,000 people are expected to attend over the weekend. The street fair will host 122 vendors and a wide range of performers.

“Someone always asks us, ‘What are you going to do?’ ” said Gonzales, keeping mum about I.B. Posse’s plans for its sculpture this weekend.

“It’s a bit of a secret motive we have so that our competition doesn’t find out what we are doing. It’s more fun (that way) and keeps the spectators interested, so they come out and are entertained.”